Two-way speech communication of two parties mutually transmitting and receiving audio signals, in particular, speech signals, often suffers from deterioration of the quality of the audio signals caused by background noise. Hands-free telephones provide comfortable and safe communication systems of particular use in motor vehicles. However, perturbations in noisy environments can severely affect the quality and intelligibility of voice conversation, e.g., by means of mobile phones or hands-free telephone sets that are installed in vehicle cabins, and can, in the worst case, lead to a complete breakdown of the communication.
Consequently, some noise reduction must be employed in order to improve the intelligibility of electronically mediated speech signals. In particular, in the case of hands-free telephones, it is mandatory to suppress noise in order to guarantee successful communication. In the art, noise reduction methods employing Wiener filters or spectral subtraction are well known. For instance, speech signals are divided into sub-bands by some sub-band filtering module and a noise reduction algorithm is applied to each of the frequency sub-bands.
However, the intelligibility of speech signals and quality of hands-free communication is still not improved sufficiently when perturbations, e.g., caused by driving and rolling noise of vehicles at high speeds, are relatively strong resulting in a relatively low signal-to-noise ratio. In particular, at transitions from verbal utterances (speech activity) to speech pauses after the encoding and decoding of speech employed in the transmission of speech from a near party to a remote party communication suffers from severe artifacts known as the gating effect. Thus, there is a need for an improved method and system for noise reduction in electronic speech communication, in particular, in the context of hands-free sets.